The present invention relates to quantum computing, and more specifically, to systems and methods for a two-qubit microwave-activated controlled phase gate.
Superconducting qubits have made considerable progress recently in experimental controls for generating a universal set of quantum gates for quantum computing. Analogous to how classical algorithms can be built from a universal logic gate, such as a NAND gate, all quantum algorithms can be constructed from a universal set of quantum gates. It has theoretically been proven that such a universal set includes arbitrary single qubit rotation gates and a two-qubit entangling gate. The quality of these gates are characterized by a metric known as gate fidelity, and how close this number comes to unity reflects how well the gate maps a complete set of input states to ideal output states.
The underlying qubit architecture determines the gates that can be practically implemented. For superconducting qubits, the single qubit gates are simple and a resolved issue; these are generated by shaped microwave pulses which are resonant with the frequencies corresponding to the qubit transitions and have resulted in gate fidelities better than 0.999. In contrast, there have been many different implementations of the entangling two-qubit gate, each with their own set of advantages and disadvantages. Some of these gates involve added circuit and control complexity for the qubit while others place stringent requirements on the integrity of different microwave control signals applied. To date, none of these approaches provide the same ease of control as the shaped microwave single qubit gates.